The present invention relates to a regulator of liquid pressure of the type used in liquid conducting systems, for example, irrigation systems with the pressure regulator maintaining a constant pressure of the liquid flowing out through it, independent from the inflowing pressure. The pressure regulator device in accordance with the present invention, apart from keeping the outlet pressure constant by-means of an adjustment of one of its components, the device works also as an antidrainage valve.
The liquid pressure regulator has five components: three main parts and two accessories. The main parts include a first part through which the liquid flows into the regulator; an intermediate part, a plunger which slides on a piston fixed on the first part, and a third part through which the liquid flows out of the regulator. The accessories include one seal and one spring.
It is important to note that the double frustoconical profile in the plunger and toroidal in the contact point of the plunger in the inlet piece and a bolt in which the plunger ends, which slides into the cylindrical cavity of the housing, giving a second support to get a coaxial sliding of the plunger on the fixed piston of the inlet part. Apart from these components, there is an alternative related to the plunger, on which a double rear bolt is foreseen: one of them is the one mentioned before, but concentric, and before this one, another bigger one is built, which leans on the internal wall of the housing and avoids liquid leakage until the desired pressure is obtained. With this, the regulator does double work: the pressure regulating valve and antidrainage valve simultaneously function, as was mentioned before.
The pressure regulator most frequently used today differ substantially from the present invention, such prior art regulators are described in U.S. Pat. Nos. 4,543,985, 5,257,646 and 5,875,815. The technical differences between the prior art regulators and the present invention are, among other things, provided by the location where the regulation of the pressure is produced. In the prior art regulators, the liquid enters the regulator through the center and is directed to the periphery by means of a deflector star which immediately diverts to the center where the regulation takes place. During the first step, the central flow moves to the periphery, and in the second step, this same flow moves from the periphery back to the center where the regulation takes place. However, the prior art regulators are significantly more complex than the present invention because they have, on average, a total of least 18 components.
In the present invention, regulation takes place during the first step when the liquid flow moves from the center to the periphery of the regulator. The liquid flow moves back to the center only when leaving or exiting the device. This fluid flow path permits the present invention to be significantly less complicated and less costly than the prior art regulators while being highly effective and efficient.
In U.S. Pat. No. 5,875,815, a pressure regulating valve is provided with a built-in antidrainage device, but, as it will be explained later, such a valve differs substantially from the present invention, including everything related to the antidrainage device. Apart from what was previously mentioned related to the central flow of this regulator, in U.S. Pat. No. 5,875,815, the antidrainage device presents the following characteristics: the plunger, or cylindrical central part, must be built in three parts; the element working as the antidrainage device is positioned permanently in the center of the flow of the fluid, which means that even after the regulator permits the fluid into the device, the antidrainage elements continue to oppose the fluid flow, thereby producing high pressure losses. In the regulator in accordance with the present invention, on the contrary, the drainage system provides that: the plunger is always built in only one piece; and the more the plunger slides within the regulator assembly, the less the plunger opposes the fluid flow, unexpectedly decreasing the pressure losses within the device.
Prior art regulators are additionally disclosed in U.S. Pat. Nos. 4,474,207 and 2,888,033. The regulators in accordance with these patents are not frequently used today because they provide inaccurate pressure regulation due to the non-coaxial sliding of the intermediate cylindrical piece with respect to the inlet piece and due to the point of contact between the plunger and the inlet piece being flat on both pieces.
One important factor affecting inaccuracy of pressure regulation is that because there is a single supporting point between the plunger and the fixed piston, the axis of the plunger is unstable and, therefore, it does not move in a coaxial manner with respect to the fixed piston of the inlet piece. This produces lateral movements or inclination. Thus, the non-coaxial movement of the cylindrical piece produces a lack of accuracy of the regulator and a high level of hysteresis.
With respect to the lack of accuracy of this type of regulator, when the axis of the plunger does not have a coaxial and aligned position with respect to the axis of the piston, the closing of the plunger over the inlet piece is not consistent around the entire perimeter and, therefore, there are pressure leaks from the inlet to the outlet resulting in the regulator being inaccurate. Further, these differences are not constant, so for the same inlet pressure, there are different outlet pressures and, therefore, inaccuracy results from this type of regulator.
With respect to hysteresis, hysteresis may be observed when the performance of the regulator is represented on a graph in which the x-axis is the inlet pressure of the regulator and the y-axis the outlet pressure of the regulator. Two curves are obtained as the inlet pressure is varied. One curve results from the increase of the inlet pressure while the other curve is obtained as this pressure decreases. The difference between these two curves is called hysteresis, as shown in Graph No. 1. The upper curve was obtained by increasing the pressure in the inlet of the regulator, while the lower curve was obtained while decreasing the pressure in the inlet of the regulator. All pressure regulators have hysteresis, but the lower the hysteresis, the more efficient the regulator will be.
However, when the movement between the plunger and the piston is not coaxial, it is difficult for the plunger to return to its original position, thus increasing the hysteresis of the regulator. To overcome these problems, U.S. Pat. No. 2,888,033 suggests a screw structure which fixes the position of the plunger thereby causing an inclination of this piece from its initial position. Also, U.S. Pat. No. 4,474,207 discloses the use of additional ribs on the housing. These ribs provide very little space (almost none) over the plunger to be effective, a structure which increases the level of hysteresis. However, if a larger space is left to decrease the level of hysteresis, lateral movements cannot be avoided.
Also, the surfaces of contact between the plunger and the inlet piece of the present invention are flat. U.S. Pat. Nos. 4,474,207 and 2,888,033 share this structural characteristic. However, the problem of accuracy occurs when flow is low because there needs to be a small and accurate closing. In this operating condition, it is found that the change of pressure from the inlet to the outlet pressure does not occur in a single point. This change in pressure occurs throughout the thickness of the plunger. This means that there is an inlet pressure on one side of the plunger and an outlet pressure on the other side of the plunger. Consequently, if the closing is flat, the decrease of the pressure from the inlet to the outlet is progressive throughout the length or thickness of that plane. This means that there is an intermediate pressure between the inlet pressure and the outlet pressure and, therefore, this intermediate pressure is directly proportional to the inlet pressure because the higher the inlet pressure is, the higher the intermediate pressure will be.
It is important to consider that the surface of the plunger which produces the opposing force of the spring is its exterior surface, without considering the surface of the thickness, because this surface receives pressure from both sides. Because the surface of the thickness is below the intermediate pressure, which varies and is affected directly by the inlet pressure, the opposing force of the regulation spring decreases with the increase of the inlet pressure. Thus, theoretically, the outlet pressure on the other side of the plunger is constant. In this manner, the regulation is ineffective and increases the level of hysteresis. With high flow, where the closing should not be narrow, this effect is not very important, even though it does exist. However, its presence with low flow is significant.
The pressure regulator of U.S. Pat. No. 4,474,207 also has five pieces and two accessories and has problems and structures that have been solved by the present invention. The inventor of this application has also filed previous pending patent applications including Argentinean Nos. P990100737, P000104751 and P010101164; and in the U.S.A., U.S. Ser. No. 09/950,482. In these pending patent applications, which present similar regulators to the present invention, one may achieve successful regulation with a double frustoconical profile in the contact point between the plunger and the inlet part, and one may also be able to maintain and slide coaxially the plunger in relation to the fixed piston. This is accomplished with the help of at least two positioning elements, which, as previously described, permit the plunger to slide and to be kept coaxially in relation to the fixed piston. Also mentioned were various specific types of positioning elements.
In the present application, different elements in these applications are presented: a new type of closure or of contact point between the plunger and the inlet piece; a new form of positioning the plunger coaxially in relation to the fixed piston of the inlet piece; and a simple change in the plunger with which we make the disclosed regulator work simultaneously as a regulator and as an antidrainage valve.
The new type of closure consists in making a toroidal profile in the inlet piece where it contacts the plunger, instead of the frustoconical profile of the previous presentations, and a double frustoconical profile in the sleeve of the plunger. Regarding the new method of positioning the plunger coaxially in relation to the fixed piston, this method consists of a bolt that continues the plunger and slides into the cylindrical cavity made with that objective in the housing.
Concerning the antidrainage system, the making of a double bolt in the rear portion of the plunger, the first prevents water drainage when touching the internal wall of the housing until minimal pressure has been reached.
It is important to clarify here that in relation to borders that the U.S. Pat. No. 4,474,207 presents one difference with the bolt of the present invention is that it is separated from the seal that serves as the first support to the plunger, at a distance seven times larger than the distance between the seal and the contact or closure point. This enables us to give it a large span so that it does not hinder the sliding of the bolt inside the cavity.
Undoubtedly, due to the larger span, the bolt will incline, but the maximum inclination of the bolt would only affect the plunger in a seventh part in the contact point. While the borders of the U.S. Pat. No. 4,474,207 are throughout the entire surface, having a direct incidence, that is 1 to 1, in that way it is impossible to enlarge the span. This will also be enlarged in the Detailed Description of the Invention.
The present invention is a pressure regulating device for liquids consisting of three principal parts. The first part is an inlet through which the liquid enters and travels to the periphery of the device through internal tubes. The first part ends in a piston, which is fixed to the same and on which a cylindrical piece slides; the second part, the plunger, closed on one end, where the bolt ends, this bolt slides within the cylindrical cavity located in the housing.
Part 2, the plunger, slides on the fixed piston of part 1, and by means of its sleeves, opens or closes the internal pipes of part 1 mentioned before, causing in this way the regulation of the outlet pressure of liquid.
Enclosing the group is part 3, the housing, which also forms, between itself and part 2 (plunger), a pipe through which liquid is led outside of the regulator. The outlet is found on the third housing part. This outlet part has, consequently, pipes that let the liquid go out of the device, a cylindrical cavity through which the rear bolt of the plunger slides, and also with the front bolt of the plunger it produces the antidrainage effect.
The regulator has these other accessories:
A spring 55, which is positioned between inlet part 1 and the cylindrical part 2. The spring is designed to maintain both parts separated and opposes to the power generated by the outlet pressure and the internal surface of the plunger 2; and
A seal that closes hermetically the chamber formed between the fixed piston of part 1 and the plunger 2.
As discussed previously, a third accessory, the positioning element, may be used. However, its use in this invention is not essential because the bolt fits the function of placing the plunger in a coaxial way in relation to the fixed piston perfectly, but if it is used it increases the effectiveness of the regulator.